This invention relates to anti-inflammatory pharmaceutical agents and, in particular, to novel compounds isolated from a natural source for the treatment of human and animal inflammatory disorders mediated by cyclooxygenase-2 (COX II) and/or 5-lipoxygenase (5-LO).
The process of inflammation entails a complex series of cellular and biochemical mechanisms orchestrated in such a manner so as to protect an organism from injury and pathogens. An inflammatory response is characterized by vasodialation, pain, swelling (edema), fever, the release of fluid transudate, and the infiltration of inflammatory cell types into inflamed tissues. Inflammation can be elicited by assorted types of insults and pathological states including acute injury (i.e., lacerations, abrasions), allergic reactions such as asthma, allergic rhinitis, and, allergic skin diseases, and immunological diseases such as rheumatoid arthritis, and some neurodegenerative disorders such as Alzheimer""s disease.
Prostaglandins (derived from eicosanoic essential fatty acids) are produced during an inflammatory response by inflammation-related biochemical pathways and are responsible for mediating the clinical manifestations characteristic of inflammation. In addition to mediating inflammation, there is some evidence that prostaglandins are involved in mediating the proliferative capacity of some cancerous cell types (Planchon, P., Veber, N., Magnien, V., Prevost, G., Starzec, A. B., and Israel, L., (1995), Life Sciences, v57, p1233). The major source for the production of inflammation-related prostaglandins is arachidonic acid. In addition, metabolites of linoleic or eicosapentaenoic acid and other related fatty acids present in dietary constituents, or found in other sources, are potential mediators of inflammation. The prostaglandins, thromboxanes, hydroxyeicosatetraenoic acids and other metabolites derived from linoeic, eicosapentaenoic, and other fatty acids can also, in principle, participate in pro-inflammatory processes (Sinclair, H. M. (1980) xe2x80x9cDrugs Affecting Lipid Metabolismxe2x80x9d (Elsevien/North-Holland, Amsterdam)). Arachidonic acid (AA) can be metabolized by one of two cyclooxygenases (COX I or COX II) producing inflammatory metabolites such as prostaglandin E2 (PGE2), PGI2, PGF2-alpha, and thromboxane (TBX). The increased production of pro-inflammatory metabolites such as PGE2 in inflamed tissues is due to the specific upregulation of COX II (Maier, J. A. M., Hla, T., Macaig, T. J., (1990), J. Biol. Chem., v265, p10805). The increased expression of COX II during an inflammatory response is believed to be induced (in part) by exposure to bacterial endotoxins and/or the release of pro-inflammatory cytokines (Isakson, P. C., (1995), Med. Chem. Res., v5, p344; Raz, A., Wyche, A., and Needleman, P., (1989), P.N.A.S., v86, p1657; O""Sullivan, M. G., Chilton, F. H., Huggins, E. M., McCall. E., (1992), J. Biol. Chem., v267, p14547), although other materials may increase expression of COX II as well.
In contrast, COX I is constituitively expressed in most tissues and has been proposed to be involved in the maintenance of physiological functions such as platelet aggregation, cytoprotection in the stomach, and in part, the regulation of normal kidney function (Prasit, P., Black, C. C., Chan, A. W., Ford-Hutchinson, J. Y., Gauthier, R., Gordon, D., Guay, S., Kargman, C. K., Lau, C. S., Li, J., Mancini, N., Quimet, P., Roy, P., Tagari, P., Vickers, E., Wong, R. N., Young, and R. Zamboni., (1995), Med. Chem. Res., v5, p364; Pinto, D. J., Pitts, W. J., Copeland, R. A., Covington, M. B., Trzaskos, J., Magolda, R., (1995), Med. Chem. Res., v5, p394; Whittle, B. J. R., Higgs, G. A., Eakins, K. E., Moncada, S., and Vane, J. R., (1980), Nature, v284, p271). Cloning of the human COX II gene has permitted a comparison between the two enzymes at the molecular level and has revealed a cassette of 18 amino acids near the C terminus of COX II that are absent in COX I (DeWitt, D. L., Bhattacharyya, D., Lecomte, M., and Smith, W. L., (1995), Med. Chem. Res., v5, p325). The differential expression of COX I versus COX II combined with differences at the molecular level suggests the possibility that compounds capable of binding to and inhibiting COX II, but not COX I could be developed.
In addition to the production of pro-inflammatory eicosanoid metabolites via the cyclooxygenase pathways, AA also serves as the source for the production of another class of inflammation-related metaboliotes produced by a family of related enzymes called lipoxygenases (5-, 12- or 15-LO). In particular, 5-LO catalyzes the first step of a biochemical cascade that culminates in the biosynthesis of a class of molecules termed leukotrienes (LT) such as LTA4, -B4, -C4, and -D4 (Sirois, P., Pharmacology of the Leukotrienes, Advances in Lipid Research, R. Paoletti, D. Kritchevesky, editors, Academic Press, 21: 79, 1985). Leukotrienes have been implicated as important mediators of inflammatory responses, such as anaphylaxis, suggesting that potent inhibitors of 5-LO would provide an approach to limit the deleterious effects of all the products of this pathway. Elevated 15-LO activity has been associated with conditions such as asthma and hypereosinophilia. Selective inhibition of 5-, 12-, or 15- LO may provide an agent with a definite therapeutic advantage.
Non-steroidal anti-inflammatory drugs (NSAIDS) such as aspirin are among the most frequently used drugs currently available. Originally, the medicinal utility of classical NSAIDS was suspected to be due to their ability to inhibit the activities of COX I (Mitchell, J. A., Akarasereenont, P., Thiemermann, C., Flower, R., Vane, J. R., P.N.A.S., (1993), v90, p11693; Meade, E. A., Smith, W. L., DeWitt, D. L., (1993), J. Biol. Chem., v268, p6610). Today, it is recognized that NSAIDS also have anti-inflammatory activity due to inhibition of COX II as well. Other biochemical activities associated with NSAIDS include inhibition of inflammatory mediators other than those mentioned above (i. e. histamine, serotonin, kinins), inhibition of oxidative phosphorylation, displacement of anti-inflammatory peptides from serum albumin, or displacement of peptides that hyperpolarize neuronal membranes in inflamed tissue (Foye, W. O. (1989) xe2x80x9cPrinciples of Medicinal Chemistryxe2x80x9d (Lea and Febiger/London)). However, inhibition of the constituitively expressed COX I by chronic use of NSAIDS leads to major side effects including the development of gastric ulceration and nephrotoxicity (DeWitt, D. L., Bhattacharyya, D., Lecomte, M., and Smith, W. L., (1995), Med. Chem. Res., v5, p325).
Therefore, development of an agent that selectively inhibits COX II would be useful to avoid the toxicities associated with COX I inhibition. The structure-activity relationship of potential inhibitors can be manipulated to produce such a desired selective effect. Modifications of some NSAIDS have also been made to increase therapeutic activity and decrease toxicity. For example, NSAIDS prodrugs such as sulindac have reduced toxicity, have improved half life, and have better solubility characteristics than the parent-type compound indomethacin. Prodrug inhibitors of mediators of inflammation may possess significantly improved pharmacological and pharmaceutical properties.
The key roles played by the AA metabolites produced by COX II and 5-, 12-, 15-LO in mediating inflammatory responses has prompted extensive research to identify compounds capable of specifically inhibiting the enzymatic activities of COX II, 5-, 12-, 15-LO, or more than one simultaneously (i.e., dual inhibitors). Compounds capable of inhibiting COX II (but not COX I) and/or 5-LO would be of great use as anti-inflammatory agents without the ensuing deleterious side effects common to most non-steroidal anti-inflammatory drugs. Alternatively, compounds inhibiting release of arachidonic acid or other fatty acids or compounds antagonizing proinflammatory cytokines would be of potential therapeutic use. Such inhibitory compounds would have great clinical utility in the treatment of such conditions as pain, fever, asthma, allergic rhinitis, rheumatoid arthritis, osteoarthritis, gout, adult respiratory disease syndrome, inflammatory bowel disease, endotoxic shock, ischemia-induced myocardial injury, atherosclerosis, and brain damage caused by stroke. Such inhibitors could also be used topically for the treatment of acne, sunburn, psoriasis, eczema, and related conditions.
This invention relates to a composition and method for treating inflammation by inhibiting the production of pro-inflammatory metabolites via the cyclooxygenase and/or lipoxygenase pathways. More specifically, this invention relates to the treatment of inflammation and inflammation related disorders through the use of compounds (and derivatives thereof) identified from a natural source.
Numerous compounds with anti-inflammatory activity have been chemically synthesized (T. Y. Shen, J. Med. Chem., 24 1, 1981) but very few anti-inflammatory agents have been isolated from various natural product sources. Although an agent such as indomethacin can trace its route of development from observations concerning abnormal human indole metabolism, the vast number of salicylic, anilino, anthranilic acid, benzothiozines, and gold compounds find their origins from synthetic medicinal chemistry. In contrast, fewer anti-inflammation agents have been discovered from natural product searches. The source, from which compounds of the invention were identified, is a natural peat bog located in south-central Washington state containing compounds derived from plant, animal, marine, and microbial sources. In addition, the peat bog environment is conducive to microbial processing of compounds originating from plant and animal sources producing a highly variable and heterogeneous mixture of potentially biologically active molecules.
Additional objects and advantages of this invention will be apparent from the following detailed description of preferred embodiments thereof which proceeds with reference to the accompanying drawings.